Explanation:
Jupiter's moon Io has active volcanoes. The
Voyager spacecraft
caught several erupting when they passed the energetic moon in 1979. In the
above picture, several of
Io's volcanoes are visible and one is seen
actually
erupting. Debris from this explosive event can be seen on the upper left of
the photo, just beyond Io's edge.
Io's volcanism is thought to be caused
by the large tidal distortions raised by
Jupiter,
Europa, and
Ganymede.
These tides stretch
Io, cause internal friction, and thus heat the
interior. The hot interior then expands and forces its
way out through volcanoes. Currently, the
spacecraft Galileo is orbiting
Jupiter and
photographing Jupiter's Galilean moons.